Backpack



FIG. 1 is a front perspective view of a backpack showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a side view thereof; and,

FIG. 4 is a rear perspective view thereof.

The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The broken lines showing the remainder of the backpack are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 